Optical signals may be used to transmit data, for example, by means of an optical fiber. To increase the quantity of transmitted data, it is known to transmit a plurality of optical signals of different wavelengths in a same optical fiber. Optical devices, such as that disclosed in relation with FIG. 1, enable to create a connection between an optical fiber and optical signal processing circuits.
FIG. 1 is a cross-section view of an optical device 1 transmitting optical signals from a single-mode optical fiber 3 to, for example, optical signal processing circuits, not shown in FIG. 1. Device 1 comprises a glass plate 5 forming an interposer between optical fiber 3 and, for example photonic integrated circuits, for example, made of silicon, not shown in FIG. 1. Plate 5 for example has a rectangular shape or a circular shape. Various elements are formed, for example by etching, on the upper surface of plate 5.
These elements include a waveguide 7 capable of transmitting a multiple-frequency optical signal received from a single-mode optical fiber 3. An optical signal demultiplexer 9 transmits, over waveguides 11, single-frequency optical signals obtained by frequency filtering from the multiple-frequency optical signal transmitted by waveguide 7. A mirror 13 interrupts each waveguide 11 and is capable of reflecting, to the outside of wafer 1, the optical signal transmitted by the corresponding waveguide 11.
The end of optical fiber 3 is arranged at the surface of an end of waveguide 7. An index-matching material 15 having a refraction index between that of the fiber and that of the material of waveguide 7, is preferably arranged between the end of optical fiber 3 and the end of waveguide 7. The path of an optical signal sent by the optical fiber is shown in FIG. 1 with arrows.
Waveguides 7 and 11 have the same characteristics. Waveguides 7 and 11 are made of a material having a larger index than the glass of plate 5. Waveguides 7 and 11 should have transverse dimensions close to that of a single-mode optical fiber, for example, in the range from 3 to 15 μm, for example, in the order of 7 μm. Such dimensions enable to minimize signal losses at the input of plate 5 and to do without using a coupler. Optical demultiplexer 9 is a device which separates on at least two output waveguides 11 at least two wavelengths of the optical signal of input guide 7.
Each mirror 13 is made of a material reflecting the concerned wavelengths, for example, made of metal. Mirror 13 is obliquely formed in plate 5 and forms with the propagation axis of waveguide 11 that it interrupts an angle in the order of 42 degrees. The upper surface of plate 5 may be covered with a cladding layer 17 transparent to the concerned wavelengths.